Fix malloc()/free() mismatch in pack_tunable.
Fix malloc()/free() mismatch in pack_tunable.

This value is deallocated by FutureImpl using free(), so it must be allocated using malloc().

StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion